In Vitro Fertilization (IVF) is a fertility treatment that helps individuals and couples achieve pregnancy. Ovarian stimulation, often called “stims,” is an initial phase of the IVF process. It involves using hormonal medications to prepare the ovaries. The goal is to encourage the development of multiple mature eggs for retrieval, which helps maximize the chances of successful fertilization and embryo development.
The Purpose of Ovarian Stimulation
Ovarian stimulation differs from the body’s natural reproductive cycle. Normally, only one dominant follicle matures and releases a single egg each month. For IVF, the goal is to produce several mature eggs in one cycle. This increased egg yield is important because not every egg will fertilize, and not every fertilized egg will develop into a viable embryo.
By stimulating the ovaries to produce multiple eggs, fertility specialists increase the chance of obtaining enough high-quality embryos. These embryos can then be selected for transfer or cryopreserved for future use, increasing the chances of pregnancy. This process condenses what would naturally occur over many months into a single treatment cycle, making the treatment more efficient.
Key Medications in Stimulation
Ovarian stimulation uses specific hormonal medications to promote follicle growth and prevent premature ovulation. Gonadotropins, such as Follicle-Stimulating Hormone (FSH) and Luteinizing Hormone (LH), are key. These injectable hormones stimulate the ovaries to grow multiple follicles (fluid-filled sacs), each potentially containing an egg. FSH primarily drives follicle development, while LH plays a role in egg maturation.
To prevent premature egg release before retrieval, GnRH (Gonadotropin-Releasing Hormone) agonists or antagonists are used. GnRH agonists initially cause a surge in FSH and LH, then suppress the body’s natural hormone release, preventing untimely ovulation. GnRH antagonists immediately block FSH and LH release for quicker suppression of premature ovulation.
The final step is a “trigger shot,” human chorionic gonadotropin (hCG), given when follicles reach an appropriate size. This injection mimics the body’s natural LH surge, prompting final egg maturation and preparing them for retrieval 34 to 36 hours later.
The Stimulation Process and Monitoring
The ovarian stimulation phase typically lasts 8 to 14 days, but individual responses vary. During this period, hormonal medications are administered, often through self-administered injections. Regular monitoring tracks the ovarian response.
Patients have frequent appointments for blood tests and ultrasounds. Blood tests measure hormone levels, especially estrogen, which indicates egg development. Ultrasounds visualize and measure growing follicles and assess uterine lining thickness. Monitoring results guide medication dosage adjustments to optimize follicle growth and prevent complications. This ensures effective ovarian stimulation and ideal timing for the trigger shot and egg retrieval.
Managing Potential Side Effects and Risks
Ovarian stimulation can cause physical and emotional changes. Common side effects include bloating, mild abdominal discomfort, and breast tenderness, largely due to hormonal changes and ovarian enlargement. Some individuals may also experience mood swings or injection site reactions like bruising or soreness. These effects are temporary and subside after the stimulation phase.
A more serious, but less common, risk is Ovarian Hyperstimulation Syndrome (OHSS). OHSS occurs when ovaries overrespond to fertility medications, causing excessive swelling and fluid leakage into the abdomen, and occasionally, the chest. Symptoms range from mild bloating and nausea to severe abdominal pain, rapid weight gain, decreased urination, and shortness of breath in severe cases. Medical teams use careful monitoring and adjusted medication protocols, including specific trigger shot choices, to minimize OHSS risk. Patients should communicate any symptoms promptly to their healthcare provider for management, which may include fluid management and rest.